Patent GB-795763-A (GB)
Title: Improved sulfonation process
IPC: C07C303/04
Filed: 1956-08-17
Abstract: Oil-soluble sulphonic acids are prepared by sulphonation of alkylated aryl hydrocarbons, in the presence of a hydrocarbon diluent oil containing substantially no sulphonatable hydrocarbon, with a sulphonating agent in proportions sufficient to provide 2 to 7 mols. sulphur trioxide per mol. of alkyl aryl hydrocarbon in the feedstock. Useful feedstocks are mono-, di-, and tri-substituted alkyl mono- and di-nuclear aromatic hydrocarbons which may include some inert or non-reactive oils, the feedstock preferably having a sulphonatable hydrocarbon content over 60 volume per cent.  In the case of mono-nuclear aromatic hydrocarbons the molecular weight of the sum of the alkyl groups preferably exceeds 240, and the molecular weight of the sum of the alkyl groups in the di-nuclear hydrocarbons is preferably greater than 180.  Active ingredients in the feedstock may comprise polypropyl benzene and toluene, triamyl naphthalene and mono- and polyalkylated naphthalene.  Suitable feedstocks may be prepared by chlorinating kerosene fractions containing straight chain paraffins having about 12 carbon atoms and then alkylating benzene using aluminium chloride as catalyst.  Propylene tetramer and butylene trimer may also be used as sources of alkyl groups.  The diluent oil is preferably a mineral oil boiling within the range of 200 DEG  to 800 DEG  F., such as a naphtha, gas oil or white oil. The removal of sulphonatable hydrocarbons may be achieved by treatment with concentrated sulphuric acid.  The resulting diluent oil contains less than 2.0 per cent, preferably less than 0.5 per cent, of sulphonatable hydrocarbon.  The preferred diluent oil is a predominantly paraffinic oil having a viscosity in the range of 50 to 350 S.S.U. at 100 DEG  F., preferably 80 to 130 S.S.U. at 100 DEG  F. The amount of diluent used should be sufficient to reduce the viscosity of the feedstock to below 450 S.S.U. at 100 DEG  F. without reducing the amount of sulphonatable hydrocarbon in the feedstock to below 30 volume per cent.  Sulphonating agents which may be used include 98 per cent sulphuric acid, oleum and liquid or gaseous SO3. When 20 to 30 per cent oleum is used, an amount sufficient to provide 5 to 7 mols. of SO3 per mol. of sulphonatable hydrocarbon is suitable.  When liquid or gaseous SO3 is used, the ratio is preferably between 2.5 to 3.5 mols. of SO3 per mol. of sulphonatable hydrocarbons.  The sulphonating agent may be applied in single or multiple batches. The reaction temperature is generally maintained within the range 32 DEG  to 175 DEG  F., a range of 65 DEG  to 110 DEG  F. being preferred.  After sulphonation, the sludge may be separated from the mixture and the sulphonic acid product may be recovered as such or may be neutralized by addition of alkali and the sulphonate extracted with alcohol.  The alkali and alcohol may be added simultaneously. Alternatively, the mixture may first be extracted with alcohol to obtain a sulphonic acid concentrate which can then be neutralised. The acid may also be neutralized with calcium hydroxide in situ in the diluent oil to provide, for example, a 30 per cent solution of calcium sulphonate in diluent oil. Suitable solvents include isopropyl alcohol, ethyl alcohol, secondary butyl alcohol, and other alcohols with or without water.  Suitable neutralization agents include Li, Na, K, Rb, and Cs hydroxides and carbonates, and Ca, Sr, Ba, and Mg oxides, hydroxides and carbonates. In a preferred method of operation, the alkylated aryl hydrocarbon, an inert diluent oil and a sulphonating agent are supplied to a reaction vessel comprising a high-speed turbo or shear mixer which is maintained at reaction temperature either by heat exchange through the walls, by cooling coils in the vessel or by external heat exchange with a pump-around system.  The mixture is reacted for 2 to 9 hours and then the sludge is removed in a settling zone.  The acid oil is freed of SO2 and then extracted with a solvent such as isopropyl alcohol, in multiple stages, if desired, at 32 DEG  to 175 DEG  F.  The extract is mixed with a calcium hydroxide-calcium chloride solution, then water and solvent are stripped off.  The mixture is agitated at 150 DEG  to 200 DEG  F. for 1 to 4 hours and then heated to 300 DEG  F. to remove traces of water, and finally filtered.  During the heating step a stream of air may be passed through the product but in this case an anti-oxidant such as an alkyl phenol should be added.  In examples: (1) a polypropyl benzene feedstock is diluted with a sulphuric acidtreated petroleum distillate boiling between 200 DEG  and 800 DEG  F., and treated for one hour at 78 DEG  F. with sufficient oleum to provide 6.6 mols. of SO3 per mol. of sulphonatable hydrocarbon; the acid oil is neutralised with sodium carbonate and extracted with isopropyl alcohol; (2) the same feedstock and diluent oil are treated with oleum at temperatures ranging from 75 DEG  to 110 DEG  F.; (3) demonstrates the direct neutralization of a concentrate obtained as in (1) with a lime-calcium chloride slurry.